Walking apparatus for excavators



April 30, 1946. T. c. MULLlNs 2,399,375

WALKING APPARATUS FOR EXCAVATORS Filed oct. 2o, 1945 2 sheets-sheet- 1fifa/07026.36

fifmwfwi" n10/VHS C. /VluLLm/s April 30, 1946. r T. c. MULLlNs v2,399,375

WALKING APPARATUS FOR EXCAVATORS Filed Oct. 20, 1943 2 Sheets-Sheet 2gyj l 26 @VQ/QZ?? THON/Q5 C. /VULLms Patented Apr. 30, 1946 UNITEDSTATES PATENT OFFICE WALKING APPARATUS FOR EXCAVATORS Thomas C. Mullins,Chcago,^-Ill., assigner to The Marion Steam ShovelCompany, Marion, Ohio,a corporation of Ohio Application october 20, 1943, serial No. 506,943

- 7 Claims. (o1. iso-s) `This invention relates to improvements inWalking apparatus of the type employed in mobile excavating machines. ofthe dip bucket or drag line type.

One form of such walking cavators of the mobile type comprises a centralbase or so-called tub which normallysupports the machine during diggingor excavating operations Aand upon which the apparatus can be turned forswinging the boom and bucket, if of the drag line type, or the stick anddipper, `if of the shovel type, into the desired positions for loading`and dumping. In moving such apparatus a pair of shoes of pontoon-likeform cooperate with the tub and are operated by crank arm mechanism forlifting the tub and machine from the ground and moving the sameforwardly a short distance and then lowering them, whereupon, bycontinued rotation of the crank arms the shoes are elevated and movedforwardly and then into contact with the ground to again lift themachine and tub and advancing the same another step.

Such walking mechanism generally has been satisfactory especially foruse with excavating machines of moderate weight, but it was found thatwhen embodied lin a machine of substantially larger capacity and greaterweight, for instance a machine having a drag bucket of twenty-ve cubicyards capacity, the conventional walking mechanism failed several timesunder conditions that. could vbe expected to be encountered frequentlyin the use of the machine. Such failures occurred notwithstanding thatthe walking mechanism of the machine was carefully de signed originallyto withstand the expected stresses and, after failure, was Vfurtherstrengthened, but without correcting the cause of the breakage andavoiding the resultant shut-down i of the machine and reduced coalproduction.

The principal object of the present invention, therefore, is to provideimprovements in walking apparatus of excavating or like machines whichwithout inordinately increasing the size of the parts of the crank armmechanisms to prevent breakage thereof, affords relative lateralmovement of the crank arm mechanisms with respect to the shoes to reduceor avoid imposition on the arm mechanism of destructive stressesresulting from the tendency of the machine to shiftlaterally undercertain conditions during walking operations, as where the shoes contactsoil affording unequal support at opposite sides of the machine.

An additional object of the invention is to provide a structureaccommodating relative apparatus for exmovementbetween crank armmechanisms and the .respective shoes o f walking apparatus, and tovprovide relatively large surfaces of bearing contact between suchrelativelymoving parts for reducing excessive wear under the large loadsimposed on such parts.

Other objects of the invention relate to various features ofconstruction and arrangement of parts which will be apparent from aconsideration of the `following specification and accompanying drawingswherein:

Figure 1 is a side elevational view of an excavating machine of the dragline type embodying improvements which are illustrative of the presentinvention. i

Fig. 2 is a top plan view of the machine shown in Fig. 1;

Fig. 3` is anV enlarged broken plan View illustrating one of the twoshoes and associated operating means therefor;

Fig. 4 is a side elevation of the apparatus shown in Fig. 3;

Fig. 5 is a top plan view of a modification of the improvements; and'Fig. 6 is a side elevation of the modification shown in Fig. 5.

In Figs. 1 and 2 of the drawings a drag line machine is shown whichcomprises a house or housing I0 within which is positioned the majorportion of the operating mechanism (not shown) including a control cabor compartment for the operator and power .units by means of which thepower operated boom ll can be raised and lowered by cables I2 andwhereby a bucket I3, provided vwith haul and hoist lines I4 and l5,respectively, can be loaded, elevated and supported by the boom as themachineis swung upon its turntable from loading to load-dischargingpositions and vice-versa. The details of such parts being well-known arenot shown in the drawings nor are the conventional power means, such asthe electric motors that supply the control and operating power andwhich are positioned within the housing l0. Whether the apparatus islelectrically operated, as may be assumed in the present instance, or isoperated by steam or Diesel' power is not important insofar as thepresent invention is concerned.

The conventional apparatus shown also comprises a tub I6 .which normallysupports the machineduring excavating operations and upon which themachine may be rotated or oscillated in swinging the housing and boomarcuately for carrying a loaded elevated bucket to and from load 'anddischarging positions.

At opposite sides of the machine are shown shoes Il which cooperate withthe tub I6 during walking operations. The conventional means shown foroperating the shoes comprise a power operated shaft I8 extending fromeach side of the housing and provided with crank arms I9 at each side ofthe machine but inasmuch as the parts of the walking mechanism ateachside of the machine are similar and areV operated in unison, only theparts at one side of the machine as shown in Figs. 3 and 4 will bedescribed.

Pivotally secured to a crank pin Illa at the end of the crank arm I9 isa leg or link 20 which,

in the form shown constitutes one side of a triangular member 2| and tothe forward apex of which is pivotally attached at 22 the lower end of alink 23 which at its upper end (see Fig. 1) is pivotally attached at 24to the exterior supporting structure 25, which in turn is secured at itsupper portion to the framework of the super-.structure of the machineand atits lower end is secured to a laterally extended portion 26 of thebase 2l of the machine.

In such types of walking mechanisms hereto fore employed, the lower endsof the links or legs 20 have been attached pivotally by suitable bearingmeans directly to the respective shoes without interposed means foraccommodating relative lateral movement vof the crank arm mechanismswith respect to the `shoes while the arms are elevating the machine. Inlarge capacity machines in particular, such as are herein underconsideration, it was found that breakage of the crank arm mechanism atone side of the ma1 chine or the other occurred notwithstanding thatthose Darts Were Originally so designed and subseu quently strengthenedto provide whatappeared to be adequate strength to withstand thestresses normally imposed thereon. However, it has `been.

found that due to the tendency of a machine to shift laterally duringwalking operations when one shoe is less firmly supported by the groundthan the other, lateral stresses were set up which caused failures evenof the strengthened cranky arm mechanisms.

During the walking operations, the shaft I8 is rotated in one direction(counter-clockwise as viewed in Figs. l and 4') which, by reason of thecontrolling action of the members 2l and 23 causes the legs 20 to movedownwardly during the rst portion of the walking operation and press theshoes I 1 into contact with the ground and, as the rotation of the shaftI8 continues .to lift the tub and machine and move it to the left, (asviewed in said figures) and thereafter to lower the tub and machine andthen lift the shoes and move the latter arcuately to the left(counterclockwise) in preparation for the next downward movementconstituting the beginning of the next walking step or cycle. Since themachine can be swung arcuately in either direction when the tub supportsthe machine and the shoes are elevated, the machine can be caused towalk in any angular direction from a given position. Such walkingoperations, as stated, have resulted in breakage of the crank armmechanism at one side of the machine or the other under conditionswherein one shoe failed to provide adequate support for the load due tothe character of the supporting earth. Under such conditions apparentlya greater portion of the work in elevating the machine was imposed onthe crank arm mechanism on the other side of the machine whichapparently set up laterally directed stresses which, with the shoesunable to shift laterally by reason of their contact with the ground,caused breakage of one or the other of the crank arm mechanisms.

For the purpose of compensating for the inability of the shoes to shiftlaterally while in contact with the ground and while offering unequalsupport for the machine during the walkingoperation and to preventthesetting up of -destructive lateral stresses in the crank arm mechanism,means have been provided to permit limited relative movement between thecrank arm structure and the respective shoes. Such lateral shifting canbe accommodated by various structures, two of which are shown forillustrative purposes in the drawin-gs.

As shown in the drawings the lower end of each crank arm 20 is pivotallysecured at 28 to a saddle bearing indicated generally by numeral 29 and'comprising a member 30 which itself is pivotally mounted at its ends inbrackets or supports 3|. Such saddle bearings 29 accommodate movement ofthe arms 20 to slightly different angular posi tions of the shoes whenpressed against the ground, but instead of being secured directly to theshoes Il as heretofore, said bearings are secured to plates 32 which areso mounted on the respective shoes that they can shift laterallyrelative to the same though limited distances when excessive lateralstresses are imposed on the crank arm mechanisms.V The plates 32 whilemovable upon the shoes are attached thereto by suitable means so thatduring elevation of the plates during walking operations the shoes willbe lifted and moved forwardly as heretofore.

The means shown in Figs. 1 to 4 for securing each plate 32 to a shoe I'l comprises a pair of cables 33 each attached to the respective end ofthe plate as by eye members 34 and to the shoe by eye members 35.Sufficient slack is provided in the cables to enable the plate to slidelaterally on the shoes to a limited extent, a few inches to a footgenerally bein-g adequate for adjustment ol the plate with respect to ashoe in response to imposed lateral stresses and hence to preventbreakage of the crank arm mechanisms from that cause. The plates 32contact relatively large portions of the surface area of the respective'shoes and hence wear of the contacting surfaces is kept at a minimum.

Upon elevation ol the plates during a walking operation, the cables 33will elevate the shoes and permit the latter to reassume normalpositions with respect to the plates but due to the slack provided inthe cables as mentioned, a slight vertical separation of the plates fromthe shoes will occur during that portion of the walking cycle. Wheresuch separation is objectionable, substantial contact between the platesand respective shoes can be maintained by any suitable means such, forexample, as shown in Fig. 4 or by the modification of the structureillustrated in Figs. 5 and 6.

In Fig. 4 there is shown a cable 36 which is attached at its ends to endportions of the shoe Il and passes tautly over a grooved cam oreccentric 31 mounted on the crank pin |9a and secured to the leg 20against relative rotation with respect to the latter.

When the crank arm mechanism is in the shoe elevating position shown inFig. 4, the eccentric 31 retains the shoe in suitably close contact withthe plate'whereby the shoe is elevated to the greatest extent forreducing drag on-the shoe the shoe within a walking cycle. Sucharrangement permits relative lateral movement of the shoes Il withrespect to the plates 32 as stated and during elevation of the shoes tothe position shown in Fig, 4, when the load is removed from them, theshoes by gravity readjust or realign themselves from a laterally orlongitudinally displaced position with reference to the plates.

The modied structure shown in Figs. and 6 eliminates the use of thecable 36 and eccentric 3l by providing a pair of transverse bars 38which extend across the upper surface of the plate 32 and are attachedat the ends to the upper surface of the shoe Il. The length of the barsand vertical spacing between the intermediate portions of the b-ars andshoes is such as to accommodate sliding movement of the plate withoutpermitting appreciable relative vertical movement between the shoes andplates whereby the latter, during the elevating portion of a walkingcycle will pick up the shoes without lost motion.

In Figs. 5 and 6 the ends of the plate 32 are shown attached to theshoes also by short cables 33 as in the structure shown in Fig. 4 and inaddition means are provided for restoring the shoes to normal relationfollowing lateral displacement thereof.

The last mentioned means shown for illustration are in the form of coilsprings 39 under compression between pairs of seat members 40 to ilsecured respectively to the shoe and plate. Upon elevation of the shoes,the springs 39 will restore the shoes to original position with respectto the respective plates following lateral displacement, should suchoccur, during the portion of the walking cycle within which the load ofthe machine is imposed upon the shoes.

While I have shown and described structures for permitting relativemovement between the crank arm mechanisms and the respective shoes whilethe latter are in contact with the earth and are supporting the weightof the machine, and have provided relatively large bearing surfacesbetween the plates and shoes for distributing the imposed loads andreducing wear of the parts between which such relative movement occurs,it will be apparent that other modication of the disclosed structure maybe utilized within the spirit of the invention.

I claim:

1. Walking apparatus for an excavating machine comprising a crank armmechanism and an associated shoe at each side of the machine, plateseach secured to one of said mechanisms and arranged to bear on the uppersurface of the respective shoes for transmitting to the latter theweight of the machine during the machine elevating and advancing portionof the walking cycle, and means comprising flexible members operativelyattaching the shoes to the respective plates whereby the latter canslide laterally of the shoes during said portion of the walking cycleand said shoes will be suspended from said plates during a succeedingportion of the walking cycle and will be free to return to theiroriginal positions with relation to the respective plates.

2. Walking apparatus for an excavating machine comprising a crank armmechanism and associated shoe at each side of the machine, a platesecured to each mechanism and arranged to make load-supporting contactwith the respective shoe during the machine elevating and advancingportion of a walking cycle, and iiexible means attaching said shoes tothe plate to accommodate limited relative movement between therespective shoes and plates during said portion of the walking cycle.

3. Walking apparatus for an excavating machine comprising a crank armmechanism and associated shoe at each side of the machine, a platesecured to each mechanism and arranged to make load supporting contactwith the respective shoe during the machine elevating and advancingportion of a walking cycle, and means comprising iiexible membersattaching the shoes to the respective mechanisms for affording relativesliding movement therebetween and for effecting elevation and advancingmovements of the shoes during the remaining portion of a walking cycle.

4. Walking apparatus for an excavating machine comprising a crank armmechanism and an associated shoe at each side of the machine, a plate onthe upper surface of each shoe Providing a relatively large area ofcontact therewith, means attaching each plate to the respectivemechanism, and flexible means at opposed portions of each plate securingthe same to the respective shoe to enable limited relative slidingmovement of the plate upon the shoe during the machine elevating andadvancing portions of a walking cycle.

5. Walking apparatus for an excavating machine comprising a crank armmechanism and an associated shoe at each side of the machine, a slidableload distributing plate on the upper surface of each shoe, meansoperatively securing each mechanism to the respective plate, and meanscomprising flexible members securing each plate to the associated shoefor limiting the sliding movement of the former with respect to thelatter and for supporting the shoes during the shoe elevating andadvancing portion of a walking cycle.

6. Walking apparatus. for an excavating machine comprising a rotarycrank arm mechanism and a ground engaging shoe at each side of saidmachine, load supporting and distributing plates, connected with therespective crank arm mechanisms for movement thereby and arranged tobear upon theupp'er surfaces of the respective shoes during the machineadvancing portion of a walking cycle, and means for connecting eachplate with its associated shoe for movement as a whole on andtransversely to said shoe during said machine advancing portion of saidwalking cycle, for preventing substantial movement of said platelengthwise of and with relation to said shoe and for causing said shoeto move with said plate during a succeeding portion of said walkingcycle.

7. Walking apparatus for an excavating machine comprising a rotary crankarm mechanism and a ground engaging shoe at each side of said machine,load supporting and distributing plates, connected wth the respectivecrank arm mechanisms for movement thereby and arranged to bear upon theupper surfaces of the respective shoes during the machine advancingportion of a walking cycle, and means for connecting each plate with itsassociated shoe for movement as a whole on and transversely to said shoeduring said machine advancing portion of said walking cycle, forpreventing substantial movement of said plate lengthwise of and withrelation to said shoe and for supporting said shoe for movement withrelation to said plate to its original position during the shoeadvancing portion of said walk. ing cycle.

:THOMAS C. MULIDIS'

